The present invention relates to a fluid cushioning apparatus, and more particularly to a fluid cushioning apparatus which itself acts as a pivoting medium of two objects having a pivoting feature.
A typical prior fluid cushioning apparatus, as shown in FIG. 1, includes a hydraulic cylinder 1, a separating piece 2 fixed to cylinder 1, a piston rod 3 and two pistons 4, 5 secured on rod 3. Piece 2 is penetrated by rod 3 and kept a liquid tight relation with rod 3. Thus, cylinder 1 is formed into two compartments 6, 7. When rod 3 is actuated by connecting rod 8 to move up or down the liquid contained in the compressed compartment will flow through a passage 9 to the other compartment. The liquid flow through passage 9 is controlled by a needle valve 10 and thus a cushioning effect is achieved, i.e. rod 3 will move slowly because piston 4 or 5 is cushioned by the compressed liquid contained in the compressed compartment. Such a cushioning device is widely used in a field which has two objects in pivoting relation and needs a cushioning result. An example of incorporating such a device is shown in FIG. 2 which shows an artificial leg 11 having a thigh part 12 and a shank part 13 pivoted together on a knee part 14. The device is incorporated within shank part 13 and connecting rod 8 is pivoted on knee part 14 so that connecting rod 8 actuates piston rod 3 up and down when thigh part 12 is lifted down and up to obtain a cushioned movement for the amputee who wears artificial leg 11. A returning spring 15 is compressed when rod 3 is urged downwardly and thus is helpful to assist the amputee to stand up. However, such a device suffers the following disadvantages. The first, such a device takes so much a volume and a weight. The second, such a device has a hydraulic liquid loss due to frequent reciprocating movements, and thus cylinder 1 is not always full of hydraulic liquid and the cushioned movement is not smooth and happens to be in vibration, and the hydraulic liquid has to be refilled from time to time. It is therefore tried by the applicant to obviate the above disadvantages.